1.Design of mucoadhesive microparticulate drug carriers(1) Methods for surface modification of microparticulate drug carriers such as liposomes or bio-degradable nanoparticles with mucoadhesive polymers were established.(2) A new method for evaluating the mucoadhesive property of polymers was developed using the Coulter counter. It was found that chitosan had the highest mucoadhesive function among the polymers tested and the degree of adhesion was dependent on the amount of chitosan on the surface of carrier particles.(3) The mucoadhesive mechanism of chitosan was suggested to be a physical entanglement of the polymer with mucus polymers.2.Enteral absorption of a peptide drug insulin encapsulated in the drug carriers(1) The blood glucose level of rats was found to be significantly decreased after administration of the chitosan coated liposomes containing insulin. The lowered glucose level was maintained for more than 12h after administration of the liposomal insulin, which suggested mucoadhesion of the chitosan coated liposomes in the intestinal tract of the rats.(2) Both mucoadhesive property of chitosan coated liposomes and protective effect of liposomal encapsulation for enzymatic degradation of entrapped insulin are important factors in insulin absorption with oral administration of insulin encapsulated in chitosan coated liposomes.